When I go to the Uffizi Pretti combo ticket I get a price of almost $100 while in the book it is $40. Can this be right? It is such a big difference.
Are you sure you're on the correct, official website?
https://www.uffizi.it/en/tickets
https://tickets.uffizi.it/event/D43F5443-D676-F857-0904-0199CA8D9B74?lang=en
The 5-day Passepartout is € 40,00 per adult (without Vasari corridor.) Annual individual or family Passepartout passes are €80,00 and €120,00 respectively.
I've a feeling you're looking at a 3rd-party site which is selling tickets for a much higher price, and whichshould be avoided.
Use only the official site I've linked above for your tickets.
Editing to add: be very careful if you're attempting to get to an official ticketing site with just a google. I'm seeing a number of 3rd-party sites which appear at the top or near the top of a google result page and which should very definitely be avoided, especially anything by Walker Tours LLC or Feel The City (which is a Walker business).